From Micro-environments to Macroscopic Effects: How the Alkaline Hydrogen Evolution Reaction Drives Cu Cathodic Corrosion

Cathodic
corrosion of copper (Cu) has posed a significant challenge
for over a century, impeding various technological progresses such
as electrochemical conversion of CO2 (eCO2RR)
into fuels and other value-added carbon products. In this study, employing
a combined density functional theory (DFT) and kinetic Monte Carlo
(kMC) simulation approach, we delve into the atomistic-level mechanism
driving this phenomenon in Cu. Our hypothesis posits the pivotal role
of the alkaline hydrogen evolution reaction (HER) in facilitating
cathodic corrosion in Cu. We rigorously develop a pH-dependent hydroxide
(OH) adsorption mechanism and calculate the equilibrium OH coverage
(θOH) at varying pH levels, the thermodynamic stability
of subsurface oxygen (Osub), as well as the Cu-vacancy
mediated diffusion of subsurface oxygens (Osub). Through
comprehensive analysis, we establish a correlation among various microenvironments,
including oxygen diffusion in subsurface layers, pH-dependent OH adsorption,
and Cu dissolution into the electrolyte as (Cu–OH) complexes.
Furthermore, our investigation explores the correlation between the
surface coordination environment of active sites and cathodic corrosion
of Cu. Finally, by integrating DFT-derived thermodynamic data into
a kMC model, we successfully predict the formation of experimentally
observed corrosion pits on Cu surfaces. This combined approach not
only advances our fundamental understanding of Cu cathodic corrosion
but also offers insights crucial for developing effective corrosion
mitigation strategies.